The vast majority of private medical insurance (PMI) policyholders are against the introduction of open referrals by Bupa, according to research by ComRes.
They felt the process would restrict patient choice while the Federation of Independent Practitioner Organisations (FIPO) also voiced concerns.
However, a majority of adults with PMI agreed that insurers should be able to direct their customers to approved consultants if it can be shown their premiums could be kept low.
Bupa has defended its policy which is part of a concerted action to reduce costs from private hospitals and practitioners.
It said initial phase patients had almost unanimously approved the scheme while it has also been supported by employee benefits consultancy Aon.
The independent research carried out by ComRes found 74% of the public who have or have previously had PMI policies confirmed they would rather see a consultant recommended by their GP than choose one from a list provided by their insurer.
Half of those with a PMI policy also said that they felt an open referral process directly threatened patient choice including 49% of those who held Bupa policies.
The provider's policyholders were also more concerned (72%) than overall PMI customers (70%) that the open referral system could prevent them from seeing a consultant who has been treating them previously.
FIPO, which recently clashed with Bupa over the insurer's decision to introduce a review process for certain types of knee surgery, argued that the open referral service does not offer value for money as it has claimed.
Geoffrey Glazer, chairman of FIPO, understood that people felt that insurers should be able to take action if it results in low premiums.
"But if Bupa really wants to demonstrate best value for its policy holders, it should state whether premiums will be lowered for those who take up an open referral policy," he said.
"Patients do not want to give up their choice of consultant for nothing.
"These restrictive policies have never sold well, as has been shown by the failed attempts by two other PMI companies who have offered similar products with substantially lowered premiums," he added.
Glazer, who represents professional independent medical organisations and specialist groups in Britain, also questioned Bupa's assertion about variation in clinical practice between specialists and urged it to "produce hard data to support the contention that this leads to worst outcomes".
Bupa countered by saying that 93% of patients taking the path so far we being given guidance and a choice of hospital and consultant, while Aon has also backed up its approach.
"Bupa's new open referral service addresses head on some of our client's key frustrations and concerns," Bryan Taylor, practice lead at Aon said.
"Under this approach we understand that all consultant and anaesthetist shortfalls will be eliminated - this is clearly a major positive for our clients.
"We also expect this approach to play an important role in controlling future claims costs, which for many of our clients, is a real concern.
"And we have received assurances from Bupa that the open referral service is not about directing members to inferior, cheaper or less experienced consultants, we understand it is about selecting the most appropriate consultant based on tangible medical evidence," he added.
